As shown in FIG. 7, cell units for use in fuel cells generally comprise a cell 2 having an electrode portion 24 which is composed of an anode 21 formed on one surface of an electrolyte 20 in the form of a plate or film and a cathode 22 formed on the other surface of the electrolyte 20, an anode side plate 3 having an anode side chamber 30 facing the anode for passing hydrogen gas or like fuel therethrough, and a cathode side plate 4 having cathode side chambers 40 facing the cathode for passing air or like oxidant therethrough. A multiplicity of cell units 10 of the structure described are arranged in layers for use in the fuel cell.
The fuel cell has fuel manifolds for supplying the fuel from outside uniformly to the anode side chambers 30 of the respective anode side plates 3 and discharging the fuel flowing through the anode side chambers 30 to the outside. The fuel manifolds are formed inside the cell units 10, or alternatively externally of the cell units. Similarly, the fuel cell has oxidant manifolds for supplying the oxidant from outside uniformly to the cathode side chambers 40 of the respective cathode side plates 4 and discharging the oxidant flowing through the cathode side chambers 40 to the outside. The oxidant manifolds are formed inside the cell units 10, or alternatively externally of the cell units.
FIG. 7 shows fuel manifolds formed inside the cell unit 10. More specifically, FIG. 7 shows fuel supply manifolds 31, 90 extending through the anode side plate 3 and the cathode side plate 4, respectively, and communicating with the anode side chamber 30 of the anode side plate 3 for supplying the fuel to the anode side chamber 30, and fuel discharge manifolds 32, 91 extending through the anode side plate 3 and the cathode side plate 4, respectively, and communicating with the anode side chamber 30 of the anode side plate 3 for discharging the fuel passing through the anode side chamber 30.
As shown in FIG. 7, a seal member 5 for preventing the fuel from leaking is disposed between the anode side plate 3 and the cathode side plate 4.
Provision of seal members requires many steps of work for forming seal grooves and installing the seal members and is therefore costly, so that it is desired to minimize the number of locations where the seal member needs to be provided.
To diminish the number of seal members 5 to be installed for the fuel manifolds, the anode side plate 3 of one cell unit 10 and the cathode side plate 4 of another cell unit 10 adjacent thereto are integrally made into a bipolar plate 8 as shown in FIG. 8. Since this structure requires no seal member 5 between the anode side plate 3 and the cathode side plate 4 of the adjacent cell units 10, the number of seal members 5 needed for the fuel manifolds can be reduced.
However, in fabricating a fuel cell with use of bipolar plates 8, it is necessary to arrange cells 2 and bipolar plates 8 alternately in layers. At this time, the cell 2 adheres to the bipolar plate 8 adjacent thereto. Accordingly, when there arises a need to replace the cell 2, the cell 2 must be peeled off the bipolar plate 8 and is therefore difficult to repair or maintain. Moreover, the cell substituted for the removed cell is likely to alter the performance depending on the state of the cell as attached to the bipolar plate 8, failing to assure the fuel cell of stabilized performance in its entirety.